The normal boiling point of bromine, br2(l), is 58.8°c, and its molar enthalpy of vaporization is δhvap = 29.6 kj/mol. (a) when br2(l) boils at its normal boiling point, does its entropy increase or decrease? decrease (δs is negative) increase (δs is positive) (b) calculate the value of δs when 1.00 mol of br2(l) is vaporized at 58.8°c.

a) increase, ΔS is positive

b) ΔS = 0.089 kJ/K

Explanation:

a) Entropy is a thermodynamic quantity which measures the degree of randomness of a system. Greater the disorder, greater will be the entropy. For different states of matter the entropy increases from solid to liquid to gas.

In the given example, when Br2(l) boils it changes into the gas phase

Br2(l) ↔ Br2(g)

Thus, entropy will increase. i.e. S(product) > S(reactant) and ΔS is positive.

b) It is given that:

Br2(l) ↔ Br2(g)    ΔH = 29.6 kJ/mol